using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.IO;

//流
namespace Stream
{
    class Program
    {
        static void Main(string[] args)
        {
            Stream2();
            Console.ReadKey();
        }

        
 
static void Stream1()
        {
            string filePath = "D:\\test.txt";
            //利用File.Open創建一個FileStream實體
            using (FileStream filestream = File.Open(filePath, FileMode.Open))
            {
                //定義字符串
                string msg = "hello world";//string msg =Console.ReadLine();
                
 
//將字符串轉化為字節數據
                byte[] msgAsByteArray = Encoding.Default.GetBytes(msg);
                Console.WriteLine("開始寫入到文件中{0}", msg);
                //將字節數據寫入到流中
                filestream.Write(msgAsByteArray, 0, msgAsByteArray.Length);
                //重置流中的位置
                filestream.Seek(0
 
, SeekOrigin.Begin);
                Console.WriteLine("寫入文件中的數據為:");
                //定義字節數組
                byte[] bytesFormFile = new byte[msgAsByteArray.Length];
                //從流中讀取到字節數據
                filestream.Read(bytesFormFile, 0, msgAsByteArray.Length);
                Console.WriteLine(Encoding.Default.GetString(bytesFormFile));

            }
        }
        /// <summary>
        /// StreamWriter與StreamReader
        /// </summary>
        static void Stream2()
        {
            string filePath = "D:\\test.txt";
            using (FileStream filestream = File.Open(filePath, FileMode.Open))
            {
                //定義字符串
                string msg = "hello world(你好)";//string msg =Console.ReadLine();
                //創建StreamWriter對象System.Text.Encoding.Default:編碼格式
                StreamWriter streamwriter = new StreamWriter(filestream,System.Text.Encoding.Default);
                Console.WriteLine("開始寫入{0}到文件中", msg);
                streamwriter.Write(msg);
                //創建StreamReader對象
                StreamReader streamreader = new StreamReader(filestream, Encoding.Default);
                //這裏將讀不到數據，因為還未寫入完成
                Console.WriteLine("寫入到文件中數據為{0}", streamreader.ReadToEnd());
                //關閉
                streamwriter.Close();
                streamreader.Close();
            }
        }
    }
}

Stream繼承結構:

C# 流